Engine sputtering/missing when hot

Post by **bullojm1** » Mon Sep 21, 2015 8:54 am

I went for a flight with a flying friend this past Saturday and upon entering the pattern and pulling the power back on downwind, the engine started to slightly sputter/miss. Now, this is certainly not the first time the engine has performed this way, and I always thought it was normal for the IO-360, as the cooling air slows down and causes some fuel to boil in the delivery lines. However, my friend insists there is something wrong.

Does anyone else running an IO-360 have the same symptoms?

Here are some facts:

1) The engine runs smooth as silk at speed. It begins to sputter on downwind as I am going about 100 kts, about to deploy the flaps.

2) One landed. the engine continues to run rough.

3) In the winter, this typically does not happen. Seems to occur only on hot days (it was 85 degrees)

4) On the initial startup and taxi, the airplane run smoothly.

5) A mag-check on the ground revealed no anomalies.

Is this something that could be fixed? I currently do not have a cooling blast tube on the fuel pump.

4)

smithhb · Post by **smithhb** » Mon Sep 21, 2015 10:01 am

Mine does the same thing. I attribute it to fuel boiling in the Airflow Performance fuel injection system in my ECI IO-360. So far, after 350 hours, it has not been a problem.

Bret

bruceh · Post by **bruceh** » Mon Sep 21, 2015 10:01 am

My IO-320 suffers from this. It doesn't sputter when flying, but as soon as you slow down on the runway the engine idles erratically and has on several occasions stopped as I'm taxiing. The only solution so far has been to keep the idle up around 1000 RPM's on the ground when heat soaked. Yesterday after coming back from Reno, it was 100+ on the ground when we landed. The engine idles OK as long as you keep the RPM's up. The downside is this is hard on the brake pads, since you can't taxi slow at 1000 RPM.

After shutdown, you can hear the fuel boiling in the injection lines. My engine idles fine at much lower RPM's when cool. I'm also thinking about adding the fuel pump cooling shroud to keep it cooler, but I'm not sure that is going to do much while taxiing. I do have the dual muffler exhaust from Vetterman, so there are two heating shrouds on the airplane and all of that heat gets dumped under the cowling. I also tried wrapping the injection spider lines with heat reflective tape. Not much difference. I'm sure the steel lines conduct the heat from the cylinders similarly with or without the tape on.

Post by **bullojm1** » Mon Sep 21, 2015 10:28 am

Thanks for the replies and confirmation guys!

I have thought about adding a shroud to my fuel pump in order to keep it's temps down. Perhaps it would cool the fuel down enough so it won't boil in the fuel delivery lines to the injector?

Also, with fall/winter flying on the horizon (sorry Bruce, I know you have no idea what this is

), I might ignore this project until next summer.